Display screen or portion thereof with a transitional graphical user interface



FIG. 1 is a front view of a first image in a sequence for a displayscreen or portion thereof with a transitional graphical user interface;

FIG. 2 is a front view of a second image thereof;

FIG. 3 is a front view of a third image thereof;

FIG. 4 is a front view of a fourth image thereof; and,

FIG. 5 is a front view of a fifth image thereof.

The broken lines showing the display screen and the remainder of thegraphical user interface forms no part of the claimed design. The outershape in broken lines of an example device forms no part of the claimeddesign. The transitional graphical user interface shown in broken linesforms no part of the claimed design.

The subject matter of this patent includes a process or period in whichan image sequentially transitions into another image. This process orperiod forms no part of the claimed design.

The appearance of the transitional image sequentially transitionsbetween the images shown in FIGS. 1-5.

CLAIM The ornamental design for a display screen or portion thereof witha transitional graphical user interface, as shown and described.